What you'll find here is that noone who has been doing this for any length of time would recommend updating to 4.3.

So people are going to try and convince you not to do it, because it's unnecessary, and detrimental. If you softmod correctly, you will have everything you need with 4.1. 4.2 and 4.3 serve no purpose other than to kill homebrew. As someone who uses homebrew why would you want to do that? You might want to spend a couple minutes reading the newbies thread in my signature.

If you are intent upon ignoring good advice: You will need to turn off any update blocking hacks you have in priiloader. Then either insert a disc with 4.3 on it or you can force it to ask by testing wifi to download it. Your HBC, and most if not all cIOSes, will be gone after.